Hypertension is a well-known risk factor for nonhereditary cerebral small-vessel disease.1 Genetic causes have been identified for hereditary cerebral small-vessel diseases: cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy;2 autosomal dominant retinal vasculopathy with cerebral leukodystrophy;3 brain small-vessel disease with hemorrhage;4 and familial cerebral amyloid angiopathies.5 Although arteriopathy in these cerebral small-vessel diseases is well documented, little is known about its genetic basis.
A cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is characterized by nonhypertensive cerebral small-vessel arteriopathy with subcortical infarcts, alopecia, and spondylosis, with onset in early adulthood.6-8 On neuropathological examination, arteriosclerosis associated with intimal thickening and dense collagen fibers, loss of vascular smooth muscle cells, and hyaline degeneration of the media was observed in cerebral small arteries.7-9 These pathological findings resemble those observed in patients with nonhereditary ischemic cerebral small-vessel disease.7-11 